Why does this async code sometimes fail, and only when not observed?

Question

This is the original code that had been running fine for a few weeks. In a test I just did, it failed 0 out of 100 attempts.

using (var httpClient = new Http         


        

Answer 1

This code:

        request.Result.Content.ReadAsAsync()
            .ContinueWith(continuationAction);

returns a task, but that task is never awaited (and no Continuation is added to it). So the item's might not get set before Task.WhenAll returns.

However, the original solution seems to have the same problem.

My guess is that you are dealing with value types, and that both have a race condition, but in the 2nd example, you copy the value types early enough (while they are still their default value) into the Tuple. Where as in your other examples you wait long enough before copying them or using them such that the problem continuation that sets the values has run.